This application claims priority to JP 2002-327793 filed on Nov. 12, 2002.
1. Field of the Invention
The present invention relates to a display film. More particularly, the present invention relates to a display film that can display an image under a luminous source such as sunlight or fluorescent light different from an image under the conditions without a luminous source.
2. Description of the Related Art
Conventionally, signs, signboards, and the like that can display an image under a luminous source such as sunlight or fluorescent light different from an image under the conditions without a luminous source have been developed. For example, Japanese Patent Application Laid-open No. 2000-204320 describes a pigment or coating material prepared by mixing a phosphorescent agent, a fluorescent/phosphorescent body, and an organic pigment and a picture drawn using the pigment or coating material. Lights emitted or reflected by these components interfere with each other to emit colors different from the light when these components are individually used.
However, to display a different image on this picture drawn using the pigment or coating material by causing the phosphorescent agent and fluorescent/phosphorescent body to emit light, an excitation luminous source other than visible rays such as black light has to be employed instead of a common luminous source such as sunlight or fluorescent light.
In addition, since this picture displays a desired image by the interference effect of light, the types and mixing ratio of the phosphorescent agent, fluorescent/phosphorescent body, and organic pigment have to be exactly selected. Therefore, this picture has problems with production efficiency and cost.
Further, since this picture comprises a color-emitting layer provided by entirely covering the surface of a phosphorescent layer, energy of the excitation light is lost in the color-emitting layer. Therefore, it is difficult to intensify the luminescence of the phosphorescent layer.
Published Japanese Translation of PCT Publication for Patent Application No. 2001-507821 and the corresponding WO 98/30998 propose a signage article comprising a translucent film having a first image and a light-filtering film having a second image and disposed on the translucent film, wherein a displayed image varies according to the correlation between the luminescence of the surface of the light-filtering film and that of the back surface of the translucent film.
However, since this signage article requires a backlighting device and external power supply for changing an image from the second image to the first image, it is difficult to make a small and thin signage article. Therefore, the desire for saving installation space cannot sufficiently be satisfied.
Published Japanese Translation of PCT Publication for Patent Application No. 2002-518208 describes a film comprising a porous film having an electroluminescent or photoluminescent surface, wherein the film allows a desired image to be seen when viewed from one side and a view through the window from the other side.
However, this film does not aim to display an image under a luminous source different from that under the conditions without a luminous source. In addition, an external power supply is required to cause the electroluminescent surface to emit light. Therefore, it is difficult to make a small image display.
The present invention provides a display film that can display an image under a luminous source such as sunlight or fluorescent light different from an image under the conditions without a luminous source, for example, at night and can provide a clear display by emitting light under the conditions without a luminous source without requiring an external device such as a power supply.
In more detail, the present invention provides a display film comprising a first display layer which has a phosphorescent material on at least a part of a surface of an opaque and nonporous substrate sheet and on which a first image visible under the conditions without a luminous source is formed, a second display layer including a porous sheet having a plurality of pores, which is disposed on the first display layer in a manner such that the second display layer partially conceals the first image and on which a second image visible under a luminous source is formed, and a transparent protective layer disposed on the second display layer.
The present invention also provides a display film comprising a first display layer which has a shade material on at least a part of the surface of an opaque and nonporous substrate sheet and on which a first image visible under the conditions without a luminous source is formed, a second display layer including a porous sheet having a plurality of pores, which is disposed on the first display layer in a manner that the second display layer partially conceals the first image and on which a second image visible under a luminous source is also formed, and a transparent protective layer disposed on the second display layer.
In this specification, an xe2x80x9cimagexe2x80x9d refers to a display to create a specific impression. Examples of images include images comprising a character, figure, symbol, or the like and images not comprising a character, figure, symbol, or the like and formed by merely the original color of the substrate sheet or by applying one color to the substrate sheet. Accordingly, there may be a case where the first display layer displays a character, figure, or the like and the second display layer is not provided with a coloring agent or the like and does not display a figure or the like at all.
In the present invention, the substrate sheet may comprise a phosphorescent material emitting light having a wavelength different from that of the phosphorescent material disposed on the surface of the substrate sheet.
The second display layer may have a coloring agent in at least a portion on the surface of the porous sheet to form a predetermined image visible in the daytime or the like under a luminous source.
The transparent protective layer is preferably composed of a material having a polymer matrix and a transparent filler dispersed therein.
The display film of the present invention is available as an image display for advertisements, signboards, billboards, or the like. The display film is particularly useful in the case where a device to illuminate the image cannot be installed due to a problem with installation space or the like.
Further details of the invention are defined in the features of the claims.